AR stands for 'augmented reality' and it's the idea that we can overlay the real world with digital objects. The first instance of mass-AR is probably Pokemon Go, though people have been trying with things like QR codes for decades, it seems. The trick is to make AR (a) useful, or at least, fun, and (b) easy. Using identifiers like QR codes have the advantage of being very precise, but you need a reader. Using GPS coordinates is easier, but less precise, and doesn't really work indoors. We'll probably find there are competing AR 'networks', each using the physical world, but overlaying different (and incompatible, naturally) interpretations. It won't be long where it will be as natural for a web site to have a GPS identifier (latitude and longitude, the way photos do now) as it is to have a URL.